The earliest known citation is from John Badcock, in Domestic Amusements, 1823 (referring to a sea voyage):"The severity of the climate having compelled them to batten down and caulk their abiding...
"Batten down the hatches" is a nautical phrase than means to secure the hatches from being accidentally opened in heavy weather. By extension, it means to get prepared for rough going.
It's "batten" down the hatches.
Meaning
Prepare for trouble.
Origin
Climate change is providing plenty of opportunity to reinforce our property against bad weather. The securing of property,...